Halide brines are commonly used in industry for various applications, drilling fluids, textile treatment, photographic emulsion, cooling systems, deicing, and dust control, for example. In the past, the production of halide brines typically required production of intermediate halide acids. The production of halide acid from halogen and hydrogen requires expensive equipment.
The process of preparing metal bromides from free metals and bromine has been reported in patent literature. For example, U.S. Pat. No. 4,138,354 discloses a process for preparing manganese bromide and cobalt bromide from elemental manganese, cobalt bromide, and bromine. The process depends upon an oxidation-reduction reaction between manganese and the cobaltous ion and the subsequent reaction of the generated cobalt with aqueous bromine. U.S. Pat. No. 4,514,374 teaches the use of a lower alkanol as a reducing agent.
U.S. Pat. No. 4,248,850 teaches the preparation of metal bromides from a basic metal compound and bromine in the presence of formaldehyde as a reducing agent. While this method affords certain advantages over prior art processes that use nitrogen-containing organic or inorganic compounds as reducing agents, namely the elimination of foaming problems due to the liberation of nitrogen gas formed during the reaction, the use of formaldehyde as a reductant often results in the presence of unreacted formaldehyde in the product mixture which is difficult to remove and thereby adds to the cost of producing the desired metal bromide products.
U.S. Pat. No. 3,431,068 discloses a method of preparing alkali metal halides by reacting an alkali metal hydroxide with an elemental halogen in a liquid (saturated aliphatic or alicyclic alcohol or ketone, or a saturated aliphatic aldehyde). U.S. Pat. No. 5,230,879 discloses a process for reducing metal halates to metal halides by reacting a metal halate with a reducing agent in an aqueous alkaline reaction medium having a pH above about 7, wherein the amount of reducing agent is sufficient to reduce substantially all of the metal halate to metal halide.
British specification No. 285,915 describes the preparation of calcium bromide by reacting a “non-acid” calcium compound (i.e. calcium oxide, hydroxide, and/or carbonate) with bromine in the presence of a reducing agent which is converted to gas and/or water. The patent describes several reaction sequences, among which are addition of the metal salt to a reaction medium comprising reducing agent, bromine, and water; and the addition of an aqueous solution of metal salt and reducing agent to an aqueous bromine reaction medium.
Similarly, U.S. Pat. No. 1,775,598 has a related disclosure to the '915 British patent. The '598 discloses the use of reducing agents which are converted into water and/or gases. These may be nitrogen-containing organic or inorganic compounds such as urea, cyanamide, ammonia, ammonium carbonate, ammonium bicarbonate, formamide, carbamates, and ammonium cyanide; or easily decomposable organic acids such as formic or oxalic acid; or ammonium or metal derivatives of these compounds (e.g. calcium nitride, metal formates, or oxalates).
U.S. Pat. Nos. 1,863,375 and 2,007,758 broadly relate to a process for preparing metal bromides employing ammonia to retard the formation of bromate and hypobromite. The '375 patent relates to the recirculation of aqueous ammonia containing metal salt solution through a tower absorber in which it is exposed to bromine vapor. While the '758 patent relates to the same general process, it is specifically concerned with a means for recovering the spent ammonia evolved from the reaction mixture. Both the patents relate to the use of ammonia as the reducing agent.
U.S. Pat. No. 2,269,733 describes the reaction of an alkali or alkaline metal compound with bromine in the presence of one of a variety of reducing agents involving several alternative reaction sequences. For example, the simultaneous addition of bromine and metal salt to another liquor, with an excess of reducing agent preferably being employed. In an alternative reaction, a two step process in which ammonia and bromine are first reacted in the presence of a mother liquor to form ammonium bromide, with the metal salt thereafter being added together with additional bromine.
U.S. Pat. No. 4,083,942 discloses the use of formic acid as a reactant, and illustrates the process with the following equation:Ca(OH)2+HCOOH+Br2→CaBr2+CO2+2H2OIn the '942 process, bromine and the alkaline compound are alternatively and incrementally added to an aqueous mixture of formic acid and a less than equivalent amount of metal compound, while maintaining the pH below 7.0.
U.S. Pat. No. 3,462,241 relates to the reaction of lime and bromine in the absence of a reductant:2Br2+2Ca(OH)2→Ca(OBr)2+2H2O+CaBr2
U.S. Pat. No. 2,415,346 discloses a process of making halogen salts of metals. Zinc bromide is made by reacting zinc chloride with hydrobromic acid under boiling temperature conditions. In the '346 process of making metal bromides, a metal salt of the type MYn is reacted with an aqueous medium of hydrogen bromide, where M is the desired metal, Y is a halogen of lower atomic weight than bromine, and n is the valence of M. The metal salt is treated with a substantially equivalent quantity of the acid in an aqueous solution with sufficient water to form a constant boiling mixture.
A problem of the high cost of production of intermediate halides during the formation of halide brines exists. The formation of these halide acids from hydrogen and halogen requires expensive capital equipment.